The proposed work consists of a broadly interlocking series of studies directed toward the elucidation of host-parasite relationships operative in certain infections. Studies of the role of cell membranes and lysosomes in the phagocytic function of human polymorphonuclear leukocytes will help define the membrane-associated events accompanying ingestion of pathogenic microorganisms. Studies of the role of cellular and humoral factors determining the fate of Candida albicans infecting the blood are near completion. Investigations are also underway to examine the phagocytosis and intracellular fate of wall-defective bacterial variants in human polymorphonuclear leukocytes. Clinical studies of the role of wall-defective variants of Neisseria gonorrhoeae in gonorrhea treatment failure and the asymptomatic gonococcal carrier state are being carried out. Studies are also planned to characterize the humoral antibody response to gonococcal L-phase variants to evaluate their potential in a serologic test for gonococcal infection. A prospective study of the frequency of detection of wall-defective bacteria in bacteremic patients is planned. Investigations of antiphagocytic surface antigens of staphylococci and their role as determinants of staphylococcal virulence are in progress.